There are several legislative and judicial interpretations for what common law is. The most common expression can be interpreted as the combination of statute law, which is created by State and Federal parliaments and other government bodies which is known as delegated legislation, and judge made law, which is written by judges in courts. The common law system originally developed in England and later being inherited by Australia in 1788. However, statute law always overrules common law when there is a clash between them. In addition, the common law can be further classified into two aspects, civil law and criminal law. “Civil law involves matters between person and person regarding the enforcement of rights and the carrying out of obligations” while civil case only results in compensations for the person who wins and liabilities for the person who lost. On the other side, criminal law contains all statute and case law in conducting a certain offence. It is enforced by government and concerned on punishment. Furthermore, with the growing concern over the inflexibility and rigidity of common law, equity has been developed by the Court of Chancery as the supplement of common law rules and procedures in two types of equitable remedies: injunction and specific performance. However, equity does not apply to criminal law as it only focuses on remedies and money damages.

The main function of judges is to interpret and apply the law to each case. However, judicial decisions made by judge are able to change the law as well. For example, judges can express their opinion in different ways relating to per-existing laws or precedents and make a new declaration on that case. In this case Donoghue v Stevenson, Mrs May Donoghue sued the manufacturer David Stevenson for negligence while Stevenson defended as no reasonable cause of action was disclosed. At that time, there was no